This invention relates to securing arrangements for securing a die cutter blanket to an anvil about which the blanket is wrapped for use in a sheet material die cutting apparatus.
Die cutter blankets are thermoset molded urethane material that wrap about steel circular cylindrical anvils. The anvils typically have a longitudinal axially extending bore and a channel in the surface thereof extending along the anvil longitudinal axis. The blankets are wrapped about the anvil and have locking projections in some embodiments. The blankets are sheet material with opposing end edges at which the locking projections are located. The ends are complementary and the locking projections engage when inserted into the channel. The locking projections interlock when inserted into the anvil channel, locking the edges to the blanket and locking the blanket to the anvil and precluding the blanket from rotating about the anvil.
U.S. Pat. No. 3,765,329 discloses one aspect of a blanket with such projections. The plastic blanket has a sheet metal inner liner. The locking projections form a two part snap in construction in which a female part receives a male part, the female part depending from the blanket at one end edge thereof with a longitudinal rounded groove and the male part is complementary to the groove and snaps into the groove. The male part may be made of metal. The female part has a metal support. The male and female parts depend from the blanket edge for insertion into the anvil channel.
Other complementary locking structures are shown in U.S. Pat. Nos. 4,073,207, 4,848,204, 3,885,486, 4,867,024, 5,078,535, 5,720,212, 5,758,560, 5,916,346 and 6,135,002. All of the above patents use inerlocking complementary depending structures which fit into the anvil channel and cooperate with each other and the anvil channel to lock the blanket ends together and to the anvil in interference fit in the anvil channel. These require the projections to be force fit into the anvil channels to obtain the locking action. Typically the projections are hammered into the channel to interlock surface features of the mating projections or to interlock the projections with the channel. In addition, the projections may be bolted to the anvil channel using brackets.
Another locking arrangement for locking blanket ends together employs interlocking interdigitated fingers which are somewhat dovetail in shape. The interlocking fingers are in the same plane as the blanket sheet material and overlie the anvil. The anvil has a channel. The interlocking fingers overlie the channel. The blanket interlocking finger end portions have a depending projection which fits within the anvil channel to preclude the blanket from rotating relative to the anvil.
The problem with the above constructions is that the locking projections that are inserted into the anvil channels mate typically in interference fit. This requires the projections to be hammered into the anvil channel. This is cumbersome. Also, to remove the blanket requires a reverse process which is even more difficult because the blanket ends need to by pried out of the anvil channel. This is a labor intensive operation and costly to implement. The present inventor recognizes a need for a simpler and easier to install and uninstall blanket locking arrangement which is faster and more economical to implement.
According to the present invention the above problems are minimized by a die cutting anvil-blanket assembly comprising a plastic material die cutter blanket lying in a plane and having opposing ends, each end having a projection depending from the plane. A roller anvil has an outer surface and a longitudinal first bore defining an axis about which the anvil rotates, the anvil having an axially extending channel in the outer surface, the blanket being wrapped about the anvil with the opposing ends and projections abutting each other, the projections being located in the channel in a locked state. A pneumatic apparatus is secured to the anvil and is coupled to the blanket for selectively securing the projections in the channel in the blanket locked state and for selectively displacing the projections out of the channel to a blanket unlocked state.
In one aspect, the anvil includes a second radial bore in communication with the channel and with the anvil first bore, the pneumatic apparatus comprising an air cylinder secured to the anvil in the first bore and associated with the second bore for selectively displacing the blanket from the locked state to the unlocked state.
In a further aspect, the pneumatic apparatus includes a spring for normally biasing the blanket in the locked state.
In a further aspect, the air cylinder includes a shaft for extending in response to applied pressurized air, and a yoke secured to the air cylinder shaft, the yoke including a member releasably engaged with the projections for displacing the projections in response to displacement of the shaft.
In a still further aspect, the air cylinder includes a shaft, the pneumatic apparatus including a spring having a predetermined bias and coupled to the anvil and to the shaft, the shaft being retracted to the locked state in response to the bias of the spring and for extension to the unlocked state in response to pressurize air applied to the air cylinder against the spring bias.
In a further aspect, an interface member is secured to the anvil and arranged to secure the air cylinder thereto.
Preferably, the interface member comprises a first member secured to the anvil in the channel and a second member depending from the first member and located in the radial bore, the second member being secured to the air cylinder.
In a further aspect, the projections at each blanket end has a recess, the recesses of the projections cooperating with each other with the blanket ends abutting in the locked state to form a single recess, the pneumatic apparatus including a member releasably engaged with the single recess for displacing the projections to the locked and unlocked states.
In a further aspect, the projections each have a slot which slots cooperate to releasably receive the member.
In a further aspect, the blanket comprises a plastic sheet member lying in a plane and having first and second opposite ends, the sheet member for wrapping about the anvil with the ends abutting. A first projection depends from the first end and a second projection depending from the second end, the first and second projections each having a recess therein distal the plane, the recesses for forming a single complementary recess extending along the blanket ends and open at one recess side facing radially away from the plane of the sheet member with the ends abutting. A first member is attached to the blanket at the first end for forming a recess wall at the one recess side.
In a further aspect, a die cutter blanket anvil has a longitudinal axis about which the anvil rotates, the blanket having opposing ends and a depending projection at each end, the projections having a common cavity, the anvil outer peripheral surface having a channel extending transverse to the axis for receiving the projections in a blanket locked state. The anvil comprises an elongated first shaft having a longitudinally axially extending first anvil bore. A plurality of second radial bores are in the first shaft, each second bore in communication with the channel and with the first anvil bore. A pneumatic apparatus is attached to the anvil in the first anvil bore at each the second radial bores, the pneumatic apparatus has a second shaft which extends in the respective second radial bore in response to a pneumatic force applied thereto. A blanket engaging device is attached to the second shaft for releasably engaging the blanket opposing ends for lifting the projections out of the channel to a blanket unlocked state from a locked state in the channel in response to extension of the second shaft. A blanket engaging member is included in the device for retaining the projections in the channel in the blanket locked state to releasably lock the blanket to the anvil.